Responses
I guess it's because he knows her situation that she hasn't even met her supposed 'husband' which is why he feels it's safe to develop feelings for her. He's not making moves on her because it'll affect her reputation tho, so at least he's ok in that aspect.
TBH, FL should be the one to turn him down hard. Even in the novel, she's been vague about it.

2MLs who still think they have a chance with a married FL who repeatedly gave hints that she's not interested are disgusting, he full on giving rapist vibes, like dude take the hint i for once want to see a 2ML move on and seriously what is he expecting from this situation? For her to cheat? Like what does he want? Because protecting her makes no sense as she has the most powerful family behind her, maybe I'm just too jaded lol but no way can I see this guy as a greenflag, I rather just him be scummy, i would have liked him more then.